1. Field of the Invention
The present invention relates to a swing arm device for a four-wheeled all-terrain vehicle.
2. Description of the Related Art
FIG. 11 is a plan view showing a swing arm device according to the prior art. An arm body 100 comprises a cylindrical front end pivot shaft 101, a drive shaft case 102 and a leg portion 105 which are extended rearward from the right and left ends of the pivot shaft 101 respectively, a cross member 104 for connecting the rear ends of the drive shaft case 102 and the leg portion 105, and a rear axle case 115 coupled to the rear end of the leg portion 105 through connecting members 106, 107 and 108. All the members 101, 102, 104, 105, 115, 106, 107 and 108 are individually manufactured and joined to one another by welding. Moreover, a bracket 116 for connecting a rear shock absorber is welded to the central portion of the rear axle case 115.
A gear case 110 for a final reduction gear and a brake case 111 are separately formed for the above-mentioned arm body 100. The gear case 110 is fastened to the rear end face of the drive shaft case 102 and the left end face of the rear axle case 115 with bolts or the like, and the brake case 111 is fixed to the right end face of the rear axle case 115 with bolts or the like. A drum type brake is provided as a braking device accommodated in the brake case 111.
As the prior art document which has described a structure other than the structure in FIG. 11, Japanese Laid-Open Patent Publication No. Hei 10-114260 has disclosed a structure in which a brake case is provided on the rear end of a drive shaft case and a gear case is fastened to the rear end of the brake case.
In the swing arm device shown in FIG. 11, the front end pivot shaft 101 and the drive shaft case 102 are joined to each other by welding. Furthermore, the cross member 104 and the drive shaft case 102 and leg portion 105, the leg portion 105 and the pivot shaft 101, and the connecting members 106, 107 and 108 are joined to each other or to one another by welding. Consequently, the number of parts is increased and a welding work takes a lot of labor and time. Moreover, if a sufficient rigidity is kept, weight is increased. Thus, there has been a problem in that it is difficult to reduce weight. Furthermore, it is necessary to assemble each part while adjusting it. Thus, an assembling work takes a lot of labor and time.
It is an object of the present invention to provide a swing arm device for a four-wheeled all-terrain vehicle in which a small number of parts are required, a welding work takes less labor and time, a light weight can be obtained, a necessary rigidity can easily be kept and an assembling work can easily be carried out.
A first aspect of the present invention is directed to a swing arm device for a four-wheeled all-terrain vehicle comprising a rear housing body, and an arm body including, a front end pivot shaft rotateably provided on a vehicle frame, a leg portion extended rearward from the pivot shaft, a drive shaft case extended rearward from the pivot shaft for accommodating a drive shaft for wheel driving, and a brake case provided at a rear end of the drive shaft case, wherein the arm body is integrally formed into one object by aluminum cast. Consequently, the number of parts can be reduced. In addition, a joining work step using welding can be omitted, manufacture can easily be performed and a light weight can also be obtained.
A second aspect of the present invention is directed to the swing arm device for a four-wheeled all-terrain vehicle according to the first aspect of the present invention, wherein a rear end of the brake case is open and a joining face for joining to a gear case of the rear housing case is formed on the rear end. In addition to the advantage according to the first aspect of the present invention, consequently, it is possible to obtain a swing arm device in which the parts related to a brake can easily be processed and the assembly of a braking device such as the assembly of a brake plate can easily be carried out.
A third aspect of the present invention is directed to the swing arm device for a four-wheeled all-terrain vehicle according to the first aspect of the present invention, wherein a rear end portion of the leg portion and the brake case are connected to each other, a rear end portion of the connected the leg portion and the brake case being formed in a flange-shape so that the joining face of the brake case and a rear end face of the leg portion are arranged on the same plane. More specifically, the rear end face of the brake case and the rear end face of the leg portion are arranged on the same plane. Therefore, it is possible to obtain a swing arm body in which processings such as casting, grinding and the like can easily be performed and a dimensional precision is excellent. Moreover, the rear end portions of the brake case and the leg portion are connected to each other by means of the flange. Therefore, it is possible to easily keep a necessary rigidity.
A fourth aspect of the present invention is directed to a swing arm device for a four-wheeled all-terrain vehicle according to the first aspect of the present invention, wherein the swing arm device being divided into the arm body and the rear housing body having the gear case to be joined to the joining face formed on the rear end of the brake case by a dividing plane which is substantially perpendicular to a shaft axis of the drive shaft, the arm body and the rear housing body being joined to each other with a bolt thereby to be separatable. Consequently, the manufacture can easily be performed. In addition, the longitudinal two-dividing structure is used. Therefore, it is not necessary to perform adjustment such as alignment of the arm body and the rear housing portion. Thus, excellent assemble-ability can be obtained. Moreover, a necessary rigidity can also be obtained. Furthermore, the seal elements for a braking device can be decreased. As a result, the number of parts can be reduced still more.
A fifth aspect of the present invention is directed to the swing arm device for a four-wheeled all-terrain vehicle according to the fourth aspect of the present invention, wherein the rear housing body is integrally formed into one object which has the gear case and a rear axle case by aluminum cast. Consequently, the number of parts can be reduced still more.
A sixth aspect of the present invention is directed to the swing arm device for a four-wheeled all-terrain vehicle according to the second aspect of the present invention, further comprising a wet multi-disc type brake in the brake case, the brake case communicating with the gear case to contain lubricating oil therein. Consequently, it is possible to efficiently cool the brake while keeping the seal-ability of the brake case.
A seventh aspect of the present invention is directed to a swing arm device for a four-wheeled all-terrain vehicle comprising, a front end pivot shaft portion rotatably provided on a vehicle frame to extend in the transverse direction of the vehicle and having a shaft axis being a center in swing with respect to the vehicle frame, a drive shaft case portion accommodating a drive shaft such that the drive shaft passes through the drive shaft case portion, a brake case portion accommodating a brake mechanism for braking rotation transmitted from the drive shaft to a rear axle, a gear case portion accommodating a reduction gear for reducing rotation transmitted from the drive shaft to the rear axle, a rear axle case portion accommodating the rear axle such that the rear axle passes through the rear axle case portion, a frame portion connecting one portion to other portion, wherein the swing arm device is divided to two parts whose joining faces are joined to each other, each of the two parts being formed such that the portions included therein are integrated with one another by aluminum cast.
Consequently, the whole is divided to two parts whose joining faces are joined to each other and each of the two parts is formed such that the portions included therein are integrated with one another by aluminum cast. Therefor, the number of parts can be reduced, a welding work takes less labor and time, a necessary rigidity can easily be kept, and an assembling work can easily be carried out.
A eighth aspect of the present invention is directed to a swing arm device for a four-wheeled all-terrain vehicle according to the seventh aspect of the present invention, wherein the drive shaft case portion is provided to extend from the front end pivot shaft portion in the same direction as the drive shaft extends for accommodating the drive shaft extending from shaft axis of the front end pivot shaft portion in the direction substantially perpendicular to the shaft axis of the front end pivot shaft portion, the brake case portion is provided to extend on the rear end of the drive shaft case portion for accommodating one portion of a transmission shaft provided to extend on the tip of the drive shaft and the brake mechanism for braking rotation of the transmission shaft, the gear case portion and the rear axle case portion is provided to extend from the rear end of the brake case portion by a certain length in the direction as the drive case portion and the brake case portion substantially extend and to extend from there in substantially parallel with the shaft axis of the front end pivot shaft portion for accommodating other portion of the transmission shaft and a bevel gear reducing rotation of the transmission shaft while transmits the rotation to the rear axle and for causing the rear axle to pass through the rear axle case portion in substantially parallel with the shaft axis of the front end pivot shaft portion, the frame portion is provided to extend from the front end pivot case portion to a tip portion of the rear axle case portion in substantially parallel to a direction in which the drive shaft case portion extends, a portion of the brake case portion and the gear case portion which includes joined portion of the brake case portion and the gear case portion is connected to a middle portion of the frame portion by expanding inward of the vehicle, and a plane by which the swing arm device is divided exists to include joining plane between the brake case portion and the gear case portion including the expanded portion, to pass through the middle portion of the frame portion, and to be substantially perpendicular to the shaft axis of the drive shaft.
Consequently, the rear end face of the brake case portion and the front end face of gear case portion constitute the joining face respectively. Therefor, by constructing the swing arm device such that brake plates and the like are inserted into the brake case portion from its joining face and transmission shaft with small bevel gear and the like are inserted into the gear case portion from its joining face, it is possible to omit opens for inserting those parts from the out side. Moreover, the rear end face of the brake case portion and the foront end face of the gear case portion are joined to each other. Therefor, the seal elements for braking can be decreased. As a result, the number of parts can be reduced.